Advice from the audio experts?

squonk · Posted: Mon Sep 15, 2014 4:47 pm Post subject: Advice from the audio experts?

A year or so ago, I built a suitcase sound system to go in the back of my Ghia. The idea being to avoid cutting holes in the car for speakers, and to have something that looked sort of retro and in keeping with the car that could easily be removed.

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The components include a Boss Audio R2002 amp, an 80 Hz Low Pass 4 Ohm crossover, a Pyle PLBW84 Blue Wave 8" 600W subwoofer and 2 PYLE-PRO PDMR5 5'' midrange drivers. The amp is fed by a Retrosound Model II radio.

It works, but the sound isn't really all that remarkable. I recognize that part of the limitation is probably the speakers I chose, and part is the fact that a convertible Ghia isn't much of a listening space. But I'm wondering if there's something I can do to the suitcase to improve the sound a bit. I've read about some people stuffing speaker enclosures with polyfill, etc. Is there something like that, or some other simple modification, I should try. I know I won't get audiophile results, but I'm willing to tweak.

Thanks in advance.
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'71 Ghia cabriolet

Kmolenda · Posted: Mon Sep 15, 2014 6:22 pm Post subject:

Speakers need a certain amount of airspace, they are all different. I would buy some 6x9 speakers and boxes, mount the boxes to the suitcase, put the grills on the outside of the case. In my opinion that stupid setup always sounded really good to me. Good highs, lows, bass. The boxes are the perfect volume for 6x9s. They are cheap too. Pi did the same thing in a boat years ago.

jpjohns · Posted: Mon Sep 15, 2014 6:40 pm Post subject:

Looks like a Boomcase. I've seen those for sale at car shows. They look too cool.

http://theboomcase.com/
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-Jared

"Scrapyards are for quitters" - Beetlenut (a Samba member)

scottz · Posted: Mon Sep 15, 2014 7:41 pm Post subject:

mountainkowboy · Posted: Mon Sep 15, 2014 9:42 pm Post subject:

I did Car Audio for 23 years...that being said, 6x9 are designed for infinite baffle, that means for a car trunk. You will limit your bass that way, unless you use a bigger box. You can find them at swap meets without any hole cut in them.
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Chuck in Socal
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71 Super Convertible...DD
78 Honda CB750K
06 Honda CR-V (wifes)
63 IH Scout 80 "Beater"

OLD VW NUT · Posted: Tue Sep 16, 2014 9:33 am Post subject:

The problem with that suitcase sound system is the subwoofer is going to be moving lots of air and 'working' those smaller speakers back and forth against their voice coils. Not good. A subwoofer needs its own enclosure - preferably a sealed one. This will give you much better tighter bass. If you want that boom box sound all the low riders have use a big ported sub box. I find those obnoxious - and they are not nearly as accurate as a sealed sub. I have an 8" sealed sub I'm going to install (some day) in my Ghia - and a pair of 6x9 3 way Infinity speakers in their own enclosures. I'm still not over the sound of my engine - it makes music I can listen to all day long.
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71 Ghia Coupe - stock body - no rust! Powered by a 2110 W/Dual HPMX 44's - Rancho Pro Street Transaxle - A/C by Gilmore

Other car - 2013 VW Golf TDI

squonk · Posted: Tue Sep 16, 2014 3:03 pm Post subject:

Thank you all for the advice.
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'71 Ghia cabriolet

philermonic · Posted: Tue Sep 16, 2014 3:12 pm Post subject:

Cool idea and I agree the sub needs to be in it's own enclosure.
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"A camel is a horse designed by a Committee"

57BLITZ · Posted: Tue Sep 16, 2014 3:45 pm Post subject:

Calculate the volume of your suitcase. You want something like .33 cu. ft. for your sub. If you case has more than that, you could remove the three speakers, line the lid of the case with 1/2" MDF, and build two small MDF boxes for your 5" speakers and glue them to the "lid panel" to sea/isolate the mids from the sub. The MDF in the lid will then provide a more solid mounting for your speakers. Seal any holes the best you can and maybe use some weatherstrip around the edge of the lid to seal the suitcase. A small hunk of MDF and an hour or two and you will be surprised at the difference!
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Jesucristo es mi Señor y Salvador!

squonk · Posted: Tue Sep 16, 2014 4:06 pm Post subject:

Thanks, 57BLITZ! I'll give that a try.
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'71 Ghia cabriolet

squonk · Posted: Sat Apr 25, 2015 10:22 am Post subject:

Thought I would close the loop on this, in case anyone else is thinking about making a suitcase sound system. I took the advice offered above and did a little additional research. I wound up enclosing each of the midrange drivers, adding poly-fill (pillow stuffing) to the suitcase at a little less than a pound per cubic foot, and sealing the case as best I could with foam weatherstripping around the edges and silicone sealant around the speakers and power/audio connectors.

The result was pretty dramatic. The sound is much cleaner now, and I can actually feel the bass on certain songs through the back of the seat. This is about as good as I'll ever need for driving with the top down, so thanks to all who offered advice.
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'71 Ghia cabriolet

varagon · Posted: Sat Apr 25, 2015 1:10 pm Post subject:

What does the updated box look like?
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1973 Karmann Ghia Convertible

squonk · Posted: Sat Apr 25, 2015 1:15 pm Post subject:

KGCoupe · Posted: Sat Apr 25, 2015 6:43 pm Post subject:

mountainkowboy · Posted: Sun Apr 26, 2015 6:58 pm Post subject:

Back in the day I used to make them out of a toolbox for truckers that drove city trucks. The only thing needed was a cig lighter to plug into. 6.5" speakers on the outside with the radio in the middle and an Hirschman amplified antenna mounted on it also. Easy to carry and not very large, it should fit in the trunk of any VW.
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Chuck in Socal
________________________________________

71 Super Convertible...DD
78 Honda CB750K
06 Honda CR-V (wifes)
63 IH Scout 80 "Beater"

squonk · Posted: Sun May 03, 2015 2:35 pm Post subject:

Here's the updated guts.

As you can see, when I was measuring the mid-range drivers in preparation for building enclosures out of MDF, I noticed that they fit very conveniently inside some won-ton soup containers I had lying around. Since those are relatively rigid, I thought I'd try them instead of reinventing the wheel. They are sealed to the inside cover of the suitcase with silicone adhesive. The poly-fill was left over from a puppet project. I'm happy with the improvement in sound, but I'll keep an eye on this thread in case the real car audio guys here have a reason that I shouldn't be using soup containers to isolate those drivers.
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'71 Ghia cabriolet

sputnick60 · Posted: Sun May 03, 2015 3:08 pm Post subject:

I'd have though the soup containers would be acoustically transparent being thin and flimsy. Or were you trying to keep the water out?
Nicholas
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'66 Karmann Ghia Cabriolet...
'65 Porsche 356C Coupe...
2005 Mecedes Benz C180 Kompressor Estate
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squonk · Posted: Sun May 03, 2015 3:18 pm Post subject:

My understanding was that the biggest problem having the midrange drivers share the same air space as the subwoofer was that the subwoofer would be pushing air around and working against the midrange drivers. I figured that anything that would separate the "air space" would be sufficient for my needs. The soup containers are certainly thinner than MDF, but they're relatively rigid when glued to the inside of the suitcase wall. Probably a simplistic understanding, but it definitely sounds better to me.
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'71 Ghia cabriolet


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